"In most of Europe the fertility rates have dropped far below replacement levels with the impending consequence of rapidly declining "native" populations, foretelling a Sweden without Swedes and a France without French. What has gone little noticed is that the Europeans who go to church are continuing to have children to such an extent that this factor alone could result in a far more religious Europe." - Stark, TC, p384-5.
Could this be one of the keys to faithful, long-term missionary work in post-Christian nations? Have babies and save the world.